In many competitive settings, consumers buy multiple product categories, and some prefer to use a single firm, generating complementary cross-category price effects. To study pricing in supermarkets, an organizational form where these effects are internalized, we develop a multi-category, multi-seller demand model and estimate it using UK consumer data. This class of model is used widely in theoretical analysis of retail pricing. We quantify cross-category pricing effects and find that internalizing them substantially reduces market power. We find that consumers inclined to one-stop (rather than multi-stop) shopping have a greater pro-competitive impact because they generate relatively large cross-category effects. (JEL D12, L11, L13, L81)

Choice in public services is controversial. We exploit a reform in the English National Health Service to assess the effect of removing constraints on patient choice. We estimate a demand model that explicitly captures the removal of the choice constraints imposed on patients. We find that, post-removal, patients became more responsive to clinical quality. This led to a modest reduction in mortality and a substantial increase in patient welfare. The elasticity of demand faced by hospitals increased substantially post- reform and we find evidence that hospitals responded to the enhanced incentives by improving quality. This suggests greater choice can raise quality.